The present invention relates to medical instrumentation; and more particularly, it relates to apparatus for obtaining bacteriologic cultures from the lower respiratory tract.
In seeking to identify the pathogenesis of lower respiratory infections in a patient, it is necessary to identify the bacteriologic contents of bronchial secretions. Initially, expectorated sputum was used to indicate the bacteriologic flora of the respiratory tract. However, the sputum may be contaminated by bacteria from the upper respiratory tract during expectoration, which makes evaluation of the brochial bacteriologic cultures misleading.
To obtain uncontaminated samples of brochial secretions, percutaneous transtracheal aspiration has been widely used. In transtracheal aspiration, a small cutaneous wheal is made just below the cricoid cartlidge. A sharp needle is then inserted through the skin, puncturing the trachea. A length of sterilized vinyl tubing is inserted into the trachea through the needle, which is thereafter withdrawn. A sterile syringe attached to the external end of the tubing by a needle provides for aspiration of secretions as the patient coughs. To avoid hematoma and subcutaneous emphysema, pressure must be applied and maintained at the puncture site with a sterilize gauze sponge, both during and for several minutes after the procedure. Although transtracheal aspiration does achieve the result of providing samples of brochial secretions with little contamination, the procedure is not suitable for patients with a high risk of bleeding from thrombocytopenia or coagulation disorders.
Another technique known in the art for obtaining diagnostic samples of bronchial secretions is the so-called "wedge" aspiration technique. In this procedure, a catheter with wire stylet is introduced into the nasopharynx through a larger, softer tube which helps to guide it through the pharynx and reduce contamination. The catheter is advanced as far as possible into the lower airways. The stylet is withdrawn, and a syringe is attached to the catheter and aspiration performed. One recognizes that the catheter has become "wedged" in an airway, by a sense of negative pressure. Positioning of the catheter in a wedged position indicates a closed system in which the catheter samples from the periphery only. After achieving the wedge position, a sample is obtained and the syringe and the catheter withdrawn.
Bronchial secretion samples obtained with the wedge technique are, however, susceptible to contamination by reason of contact of the open ended catheter with the walls of the upper respiratory tract during insertion of the catheter. Accordingly, a gram stain must be made immediately to assess the validity of the specimen obtained. If the gram stain of a specimen reveals a variety of organisms and/or many squamous epithelial cells, the specimen is highly probably contaminated with upper respiratory flora. In such case, the specimen is discarded and a new sample obtained and gram stained. The gram stain is a relative insensitive technique for determining the degree of contamination. The gram stain may appear acceptably uncontaminated on the same sample that the culture is contaminated.
Another technique for obtaining bronchial secretion samples for culturing is that of bronchial swabbing. In this technique, a cotton wool swab on the end of a wire is contained within a glass carrier tube having glass beads fused on the outside surface. The swab and glass carrier tube are passed down a bronchoscope with the swab retracted. The glass beads prevent contact between the open end of the carrier tube and any bronchial secretions present on the inner wall of the bronchoscope. The swab is extended out the open end of the glass carrier tube and the bronchial mucosa is swabbed. After swabbing, the swab is retracted and the glass carrier tube is removed from the bronchoscope. The open distal end of the carrier tube is plugged pending bacteriological examination.
It has been found, however, that the bronchoscope technique, too, allows the bronchial secretion samples to be mixed with bacteria. Accordingly, in a further attempt to obviate the contamination problem, there has been designed a bronchial secretion sampling device for use in conjunction with a fiberoptic bronchoscope. The sampling device consists of inner and outer telescopic catheters adapted for passage through a fiberoptic bronchoscope. The distal end of the outer catheter is capped with a non-toxic water soluble plug. A retractable brush is carried within the inner catheter. To obtain a bronchial secretion sample, the telescoping catheters are advanced beyond the tip of the fiberoptic bronchoscope and the distal plug removed by actuation of the inner catheter. Afterwards, the specimen brush is extended and a specimen obtained. The device is then retracted through the bronchoscope.
Another related technique proposed for obtaining uncontaminated bronchial secretion samples is the use of a small catheter capped with Gelfoam which is introduced through a fiberoptic bronchoscope. The Gelfoam dissolves in the tracheobronchial tree or is coughed up. Although this technique has proven more reliable than other techniques, it suffers from the disadvantage of being relatively expensive since the procedure is performed by a medical specialist using expensive equipment. Accordingly, there is a need for a simple, reliable method and apparatus for obtaining uncontaminated bronchial secretion samples for bacteriologic study.